1. Field of the Invention
The present invention relates to a semiconductor sensor device which can be used as, for example, a pressure sensor for detecting an intake pressure of an engine in an automobile.
2. Description of Related Art
FIG. 15 shows the constitution of a conventional intake pressure sensor for an automobile. A pressure sensitive element unit 101 is attached to one side of a ceramic substrate 100. The pressure sensitive element unit 101 includes by a sensor chip 101a and a glass base 101b and detects pressure of a medium to be measured (intake air of an engine). An IC (Integrated Circuit) chip for a signal processing circuit 102 is attached to other side of the ceramic substrate 100. The IC chip for a signal processing circuit 102 and the pressure sensitive element unit 101 are electrically connected to each other by wiring formed on the ceramic substrate 100 and bonding wires 103 and 104. A sensor signal in response to pressure detected by the pressure sensitive element unit 101 is outputted from the IC chip for signal processing circuit 102.
The ceramic substrate 100 is attached to a case 106 in which a terminal 105 is insert-molded. One end of the terminal 105 is electrically connected to the IC chip for signal processing circuit 102 via a bonding wire 107 and wiring on the ceramic substrate 100. The other end of the 10 terminal 105 is exposed at a connector unit 106a of the case 106. Electric conduction to outside is performed at the other end of the terminal 105.
An upper lid 108 and a lower lid 109 having a pressure introducing hole 109a are attached to the case 106. The pressure is introduced from the pressure introducing hole 109a of the lower lid 109 to a pressure receiving chamber 110 and the introduced pressure is detected by the pressure sensitive element unit 101. Further, the upper lid 108, the lower lid 109 and the case 106 are constituted by resin. The upper lid 108 and the lower lid 109 are fixedly adhered to the case 106 by an adhesive agent 111. Also, the ceramic substrate 100 is fixedly adhered to the case 106 by the adhesive agent 111. Due to fixation using the adhesive agent, the pressure receiving chamber 110 and a chamber (circuit chamber) 112 where the IC chip for signal processing circuit is disposed, are airtight. Further, an air vent hole 108a for escaping air from the inside during heating and curing operation, that is formed at the upper lid 108, is sealed by the adhesive agent 111.
A medium to be measured (air) introduced from the pressure introducing hole 109a includes exhaust gas and acidic condensed water produced by cooling the exhaust gas. Therefore, by providing the pressure sensitive element unit 101 for detecting pressure and the IC chip for signal processing circuit 102 for carrying out signal processing at separate chambers, the IC chip for signal processing circuit 102 can be protected against a contaminated environment of the pressure receiving chamber 110.
However, in order to provide the pressure sensitive element unit 101 and the IC chip for signal processing circuit 102 in separate chambers and maintain them in an airtight state, in addition to the airtight adhesion of the lower lid 109 and the case 106, airtight adhesion must be achieved between the upper lid 108 and the case 106, between the ceramic substrate 100 and the case 106 and at the air vent hole 108a in the upper lid. This is problematic in view of airtight reliability and complication of structure. Further, as a device capable of promoting the airtight reliability, there has been disclosed a device having the constitution where a metal diaphragm is used and displacement of the metal diaphragm is transmitted to a pressure sensitive element unit by silicone oil in Japanese Patent Application Laid-Open No. H.7-243926. However, when silicone oil is used, detection accuracy of pressure is lowered by thermal expansion thereof.
It is an object of the present invention to provide a semiconductor sensor device capable of protecting an IC chip for a signal processing circuit against a contaminated environment and still perform high accuracy detection without the need of providing a pressure sensitive element unit and the IC chip for signal processing circuit at separate chambers.